Pressure Reducing Second Stage for Underwater Use

ABSTRACT

A pressure reducing second stage for underwater use includes a case provided with a breathing gas inlet, with an inhalation/exhalation port and with an exhaled gas exhaust outlet with a non-return valve, the gas inhalation/exhalation port being connected to a mouthpiece tube, the breathing gas inlet in the case being connected to a breathing gas pressure reducing device provided with a hollow cylindrical element or pipe, which has a breathing gas inlet port communicating with a gas supply conduit through a valve which is interposed between the supply conduit and the mouthpiece tube, the case being provided with a pressure sensitive means device for controlling the opening/closure of the valve. The breathing gas inlet in the case is provided in its lower portion and the hollow cylindrical element is connected to the inlet on the case such that its axis is substantially vertical, when used in the upright position.

The present invention relates to a pressure reducing second stage forunderwater use.

Breathing gas supplying devices or pressure reducing second stages forunderwater use are known which are connectable to pressure reducingfirst stages intended to reduce the high pressure (200-300 bar) of abreathing gas contained in a tank, usually a diving cylinder, to apredetermined intermediate value, which second stages reduce thepressure of the gas from said intermediate value to a valuephysiologically suitable for breathing.

A second stage supplying breathing gas for underwater use comprises acase with an inner chamber provided with:

-   -   a pressurized gas inlet connectable, through a gas supply        conduit or hose, to a pressure reducing first stage, which inlet        is provided with a device with a valve reducing the pressure of        the gas entering said chamber,    -   an inhalation/exhalation port through which the breathing gas        supplied in the inner chamber of the case is inhaled by the user        and through which the user supplies the exhaled gas into the        chamber, which port is connected to a inhalation/exhalation        mouthpiece tube,    -   an exhaled gas exhaust outlet provided with a non-return valve.

U.S. Pat. No. 4,002,166 describes a pressure reducing second stageprovided with a bypass tube for conveying the incoming breathing gasafter opening the reduction valve, directly from the supply conduit tothe inhalation/exhalation mouthpiece tube, by-passing the inner chamberof the case.

The second stage provides the bypass tube, outside the case, to have aconnection tangent to the mouthpiece tube and that provides a vane withan adjustable angle to be provided inside the mouthpiece tube.

Patent EP 937640 describes a pressure reducing second stage wherein thebypass tube is formed integrally inside the case of said second stage.

In known pressure reducing second stages for underwater use, providedwith the bypass tube or not, considering the second stage used by a userin the upright position, the breathing gas inlet is placed on the caseon the right or left of the inhalation/exhalation port connected to ainhalation/exhalation mouthpiece tube, and said second stage isconnected to a pressure reducing first stage for a gas contained in atank, usually a diving cylinder, through a gas supply conduit or hosethat passes above the right or left shoulder of the user, when the gastank is worn on the user back.

Such configuration of the second stage, with the gas inlet on the caseat the right or left of the inhalation/exhalation port, is particularlyuncomfortable when the breathing gas tank, generally a diving cylinder,is not worn on the back but it is placed at the right or left side ofthe user that is when the pressure reducing first stage connected to thegas tank is in a position considerably lower than the user mouth havingto hold, by a mouthpiece connected to the inhalation/exhalationmouthpiece tube, the pressure reducing second stage, such to make itpossible to breath underwater.

In this case the relative position of the breathing gas tank and of thescuba diver mouth are such that it is almost impossible to find a pathof the gas supply conduit or hose connecting first and second stages insuch a manner not to have a twisting effect thereon, resulting in theuser being uncomfortable, except taking a very long hose (withconsequent adverse effects on ergonomics, drag in water, costs) or usinga joint (with consequent adverse effects on costs and reliability).

Generally in order to overcome such drawback gas supply conduits orhoses are used having such a length to pass behind the user head and toreach the user mouth not from the bottom but from the side, of the userface, such that the end portion of the supply conduit connected to theside inlet provided on the case of the second stage is substantiallyhorizontal and it does not generate rotations of the second stage thatmake holding of the inhalation/exhalation mouthpiece tube in the usermouth little comfortable and therefore making breathing underwaterlittle comfortable. This however results in an increase in drag due to agreater friction in water.

Another known solution to overcome such drawback is to place between theside inlet of the case and the supply conduit or hose a L-shaped jointallowing the second stage to be kept in the proper position in the moutheliminating the twisting effect exerted by the supply conduit or hoseconnected to said second stage.

However such solution has the drawback that the joint is a potentialpoint of failure or leakage that may cause breathing gas to escape withalso serious consequences if the user is underwater far away from thesurface.

Moreover it is known that the configuration of the second stage with gasinlet on the case at the right or left of the inhalation/exhalation portis particularly uncomfortable when the second stage is used as asecondary gas source that is as a source of gas to be supplied to asecond scuba diver.

It is a common practice, when underwater, to use a diving regulatorcomposed of a pressure reducing first stage connected through hoses totwo pressure reducing second stages, so called “octopus” configuration,one of which is used by the scuba diver carrying the diving regulatorfor breathing and the other one is carried as an emergency and it isused, if necessary, to supply breathing gas to a second scuba diver indifficulty, for example a second scuba diver having his/her divingregulator not operating or having depleted his/her personal gas supplycontained in the diving cylinder. In such situations the scuba diverwith enough gas supply gives his/her secondary second stage to the otherscuba diver in difficulty placed in front of him/her or by his/her sidebut it is known that the position of the gas inlet on the case on theright or left of the inhalation/exhalation port does not facilitate suchoperation since the hose connecting the first stage and the secondarysecond stage, in order to allow such operation, not only has to be longenough but has also to follow a S-shaped path, with consequent adverseeffects on ergonomics.

Currently although the efforts for improving the operating conditions ofthe pressure reducing second stages, above all as regards the usereffort in inhaling and exhaling the known pressure reducing secondstages have not completely achieved optimal operating conditions.

Such optimal conditions consist in making the breathing effort inunderwater condition, as much similar as possible to the one necessaryin normal environment conditions. On one side the user has not toperform suck efforts for inhaling the supplied air, but on the otherside the latter has not to be supplied at an excessive pressuretherefore air being forced into the user respiratory tract.

The invention aims at overcoming the drawbacks of the known pressurereducing second stages, by providing a pressure reducing second stagethat is simple and inexpensive to be manufactured and adjusted, that canbe used comfortably by the user without the need of complicating theconfiguration of diving equipment with elements such as long hoses, orjoints, while optimizing ergonomics and decreasing drag in water.

The aim of the present invention is also to make the breathing morecomfortable as possible making the breathing effort as much similar aspossible to that of normal environment conditions.

The aim of the present invention is also to provide a pressure reducingsecond stage easy and comfortable to be used as a secondary second stagefor breathing gas, thus making the breathing gas supply to a scuba diverin difficulty more safe and comfortable, with the consequent advantageof reducing panic and stress in water.

A further aim of the present invention is to provide a pressure reducingsecond stage wherein both the gas inhalation and exhalation phases arefacilitated, thus allowing inhalation and exhalation effort to bereduced. The invention achieves the aims described above by a pressurereducing second stage for underwater use comprising the combination ofcharacteristics of claim 1.

Said combination of characteristics comprises:

-   -   a case provided with a breathing gas inlet and with an        inhalation/exhalation port through which the gas supplied into        the case is inhaled by the user and through which the user        supplies the exhaled gas into the case, said case being provided        with an exhaled gas exhaust outlet with a non-return valve,    -   the gas inhalation/exhalation port being connected to an        inhalation/exhalation mouthpiece tube through which the        breathing gas is inhaled by the user and through which the gas        is exhaled into the case,    -   the breathing gas inlet in the case being connected to a        breathing gas pressure reducing device provided with a hollow        cylindrical element or pipe, which hollow cylindrical element        has a breathing gas inlet port communicating, through a valve,        with a gas supply conduit, which valve is interposed between        said supply conduit and said inhalation/exhalation mouthpiece        tube for said breathing gas,    -   said case being provided with pressure sensitive means for        controlling the opening/closure of said valve,    -   and wherein the breathing gas inlet in the case is provided in        the lower portion of said case, considering the second stage        used by a user in the upright position and said hollow        cylindrical element of the pressure reducing device being        connected to said inlet on the case such that its axis is        vertical or substantially vertical with reference to the upright        position of the user, that is substantially parallel to the        longitudinal axis, or cranio-caudal axis, that is to the        intersection of the sagittal plane with the coronal plane of the        user body;

a bypass tube, supplying said breathing gas from the pressure reducingdevice directly into the inhalation/exhalation mouthpiece tube, thebypass tube being connected, at one end thereof, to an port provided onthe shell wall of the hollow cylindrical element of the pressurereducing device, and at the opposite end to an port provided on theshell wall of the inhalation/exhalation mouthpiece tube.

By means of such characteristic the use of a second stage implementedaccording to the present invention is particularly advantageous if usedfor reducing the pressure of a breathing gas contained into a tankcarried on one side of the user since the gas supply conduit or hose canconnect the second stage to the pressure reducing first stage providedon the tank in a substantially straight manner without being bent, thusavoiding both the interruption of the gas flow due to clogs and the riskof moving the second stage from the proper position in the user mouth,making its use little comfortable.

The second stage implemented according to the present invention isadvantageous also if used for reducing the pressure of a breathing gascontained in a tank carried at the front of the user, for exampleattached to the buoyancy control device, since it allows the gas supplyconduit or hose to connect the second stage to the pressure reducingfirst stage, provided on the tank, without clogging the hose, forexample said hose following a substantially U-shaped path, leaving, atthe same time, complete freedom of movement to the user.

The bypass tube allows the gas inhalation action to be facilitated,making the breathing action more comfortable and physiologicallysuitable.

According to another characteristic of the present invention, in orderto facilitate the gas exhalation at any depth the second stage is usedand in order to make it as much similar as possible to natural breathingwhen out of water, said case is provided with a second exhaled gasexhaust outlet with a non-return valve.

Said two outlets can be placed at the sides of the breathing gas inletin the case connected to said hollow cylindrical element of the pressurereducing device.

As described in more details below, in order to convey the gas escapingfrom the bypass towards the user mouth, in said second stage of thepresent invention, in the inhalation/exhalation mouthpiece tube there isprovided a baffle tongue placed substantially diametrically with theorientation transverse to the axis of the bypass tube and with extensionsubstantially parallel to the axis of said inhalation/exhalationmouthpiece tube.

The function of said baffle tongue or tongue is to convey the flowsupplied through the bypass tube towards the mouthpiece such to improvethe comfort of the second stage.

In one embodiment said tongue is provided substantially at a levelcoinciding with the central diametral position of the mouthpiece tube orat an intermediate level between said central diametral position and theupper semi-circumference with reference to the second supply stage inthe condition worn by the user and with the user in the uprightposition.

In particular in said worn and upright position of the user the tongueextends substantially horizontally or parallel to the transversal planeof the user head according to the medical definition of said planeand/or parallel or coinciding with the diametral plane coinciding withthe greater diameter of the mouthpiece in the condition mounted on theinhalation/exhalation mouthpiece tube.

According to a characteristic said tongue axially extends from aposition where it substantially overlaps the outlet port of the bypasstube in the inhalation/exhalation mouthpiece tube, with one end thereoffacing towards the inside of the pressure reducing second stage, up tothe opposite end region of said inhalation/exhalation mouthpiece tube,that is facing the user and intended to be coupled to a mouthpieceelement.

According to variant embodiments it is possible to provide differentconfigurations of the tongue.

According to further variant embodiments, the tongue can be perfectlyflat or can have a curved pattern according to one of the two axial andradial directions or according to both the directions and with radii ofcurvature different from each other and constant or variable along theangle extension of the curved shape.

Still according to further variant embodiments the tongue can also endwith a substantially diametral leading edge, in the region downstream ofthe outlet port of the bypass tube in the inhalation/exhalationmouthpiece tube and it can extend till overlapping said outlet port byan appendage extending said leading edge of the tongue.

According to further characteristics said appendage can have differentshapes and dimensions according to one embodiment it has a shape like acap or half-shell.

In one embodiment, in particular said rear appendage has a firstcurvature according to one axis parallel to the axis of theinhalation/exhalation mouthpiece tube having a predetermined lengthsubstantially corresponding to the axial distance of the outlet port ofthe bypass tube in the inhalation/exhalation mouthpiece tube from therear side of the tongue and an end portion with a cap-like shape.

As an alternative said extension has only one radius of curvature arounda single axis oriented in the diametral direction of theinhalation/exhalation mouthpiece tube, or in the direction parallel tothe tongue and to the rear edge thereof, such that the appendage has acurved pattern of the end radially aligned with the outlet port of thebypass tube in the inhalation/exhalation mouthpiece tube.

Also in this case the appendage can have a plan shape or a planprojection shape substantially rectangular or tapered or curved at thefree end.

According to a further characteristic the tongue can be mountedremovably in the inhalation/exhalation mouthpiece tube by means ofcooperating means coupling it with the inner shell wall of saidinhalation/exhalation mouthpiece tube.

In one embodiment the tongue can be coupled by snap fit, form fit, byforce fit or by means of mutually removable locking means into two axialstraight guides provided along the inner shell wall of theinhalation/exhalation mouthpiece tube, on two diametrically oppositesides of said wall and each one of said guides is intended to house thecorresponding axial peripheral edge of the tongue.

In the case of a removable mounting it is possible to provide a kitcomprising the pressure reducing second stage according to the presentinvention and a series of different tongues that have different shapeand dimension characteristics and that can be mounted alternativelyinside the inhalation/exhalation mouthpiece tube.

This allows the behavior of the second stage to be easily adjusted in away corresponding to the personal needs of the user.

As an alternative to the tongue described above, according to oneembodiment of the present invention a part of the port provided on theshell wall of the inhalation/exhalation mouthpiece tube putting thebypass tube in connection with said mouthpiece tube is surrounded by awall protruding inside the mouthpiece tube and that curves in thedirection of the port of the mouthpiece tube opposite to the port forthe connection with the case, such to form a cap extending above saidport in the shell wall of the mouthpiece tube and conveying thebreathing gas flow coming from the bypass tube towards the user mouth.

According to another embodiment said cap-like wall extends for a givenportion in the longitudinal direction inside said inhalation/exhalationmouthpiece tube partially surrounding the port provided on the shellwall of the inhalation/exhalation mouthpiece tube, and bending in thedirection of the port of the mouthpiece tube opposite to the port forthe connection to the case such to form inside said mouthpiece tube atube extending in the longitudinal direction of the mouthpiece tube andplaced at the lower shell wall of the inhalation/exhalation mouthpiecetube.

These and other characteristics and advantages of the present inventionwill be more clear from the following description of some embodimentsshown in the annexed drawings wherein:

FIG. 1a is a front view of a known pressure reducing second stageprovided with a bypass tube,

FIG. 1b is a broken plan view of one embodiment of a known pressurereducing second stage provided with bypass tube outside the case,

FIG. 1c is a partially sectional top view of one embodiment of a knownpressure reducing second stage provided with bypass tube integratedwithin the case,

FIG. 2 is a perspective view of a second pressure reducing second stageprovided with a bypass tube according to one embodiment of the presentinvention,

FIG. 3 is a side view of a pressure reducing second stage provided witha bypass tube according to one embodiment of the present invention,

FIG. 4 is a bottom view of a pressure reducing second stage providedwith bypass tube according to one embodiment of the present invention,

FIG. 5 is the inhalation/exhalation mouthpiece tube and the outlet ofthe bypass tube of a pressure reducing second stage provided with saidbypass according to one embodiment of the present invention,

FIGS. 6-10 are side sections of different embodiments of the outlet ofthe bypass tube of a pressure reducing second stage provided with saidbypass tube according to the present invention.

FIGS. 11 and 12 are a section according to an axial plane of theinhalation/exhalation mouthpiece tube and a perspective section of afirst variant embodiment respectively wherein in the inhalationmouthpiece tube a diametral tongue is mounted substantially oriented inthe axial direction of said inhalation/exhalation mouthpiece tube,

FIGS. 13 and 14 are like FIGS. 11 and 12 one variant of said tongue.

FIGS. 15 to 17 each one is a top plan view of one of three differentembodiments of the tongues.

FIGS. 18 and 19 are a top and bottom perspective view of a series oftongues having different dimensions and made according to a furtherembodiment substantially corresponding to that of FIGS. 13 and 14.

FIGS. 20 and 21 are views similar to those of FIGS. 18 and 19 with afurther variant embodiment of the baffle tongue.

With reference to FIGS. 1a, 1b, 1c they show a pressure reducing secondstage 1 for underwater use provided with a bypass tube 101, according toprior art.

The function of the pressure reducing second stage for underwater use isto reduce the pressure of breathing gas coming from a pressure reducingfirst stage and to supply it at ambient pressure depending on how deepthe scuba diver is.

A pressure reducing first stage for underwater use allows high pressureof air contained in the diving cylinder (200-300 bar) to be reduced toan intermediate pressure of 8/10 bar higher than ambient pressure. Thesecond stage, connected to the first stage, therefore allows pressure tobe further reduced.

Such as shown in FIGS. 1b and 1c said second stage 1 is composed of acase 106 containing pressure sensitive means for controlling theopening/closure of a valve of a device reducing the pressure of abreathing gas conveyed in said device through a supply conduit 103, froma pressure reducing first stage (not shown) connected to a breathing gassource, generally a diving cylinder.

As it is known the pressure reducing device of the second stage,connected to an inlet provided on the case 106, comprises a hollowcylindrical element 107 or pipe, with a breathing gas inlet port 117communicating, through a valve, with a gas supply conduit 103 connectedto a pressure reducing first stage (not shown).

Such as shown in FIG. 1b in second stages according to prior art all ora part of the hollow cylindrical element 107 is provided, consideringthe second stage worn by a user in the upright position, on a sideportion of the case 106, like a cylindrical extension of the sideperipheral wall of the case itself.

Otherwise such as shown in FIG. 1c the hollow cylindrical element 107 isprovided integrated within the case, made as a hollow side protrusion ofthe case itself, extending in a radial direction, such that thebreathing gas inlet port 117 of the hollow cylindrical element 107 isformed on the wall of the case 106 itself.

At the breathing gas inlet port 117 a seal fastening terminal can beprovided, for example like a bushing, for connecting said supply conduit103 with said hollow cylindrical element or pipe 107.

Inside the hollow cylindrical element 107 a shutter 108 for a valve seat104 is slidably mounted, particularly a piston-like shutter withenlarged head connected as one piece with a stem engaging in a holeprovided on a wall opposite to the breathing gas inlet port 117.

The valve seat 104 is composed of a radial narrowing, inside the hollowcylindrical element 107, defining an aperture, along the centrallongitudinal axis of said hollow cylindrical element 107, with sharpedges that can cooperate with the surface of the head of the shutter 108such to guarantee said seat 104 to be perfectly sealed when the shutteris in the closing position that is abutting against the valve seat 104.

A spring 109 urges the shutter 108 with a predetermined force in thefirm closing direction. The shutter 108 is pivoted, in a known manner,to a lever 110 that is oscillating and that is operated by a deformablediaphragm 111 forming a part of the outer wall of the case 106.

The case 106, through a port, communicates with an inhalation/exhalationmouthpiece tube 102 through which the breathing gas inhaled by the useris exhaled into the case 106.

The inhalation/exhalation mouthpiece tube is provided with a mouthpiece105.

In prior art only one exhaust outlet 113 is provided on the case 106 forthe exhaled air that is supplied into the case 106 through themouthpiece tube 102 and the inhalation/exhalation port.

Said outlet is provided with a non-return valve 123, like a membrane,opening as the pressure inside the case 106 increases due to the gasflowing during the exhalation phase and that is kept in the closedcondition by the elasticity of the material said non-return valve 123 ismade of.

During the inhalation phase the vacuum generated inside the case 106causes the diaphragm 111 to push on the lever 110 acting against elasticmeans 109, that is the spring, and it moves the shutter 108 away fromthe valve seat 104, in the opening position, therefore the pressurizedgas, from the supply conduit 103 can enter, from the inlet port 117,through the valve seat, into the hollow cylindrical element 107 of thereducing device and it can goes out from an outlet port 112, provided onthe shell surface of said hollow cylindrical element 107, to which adedicated supply conduit 101, so called bypass tube, is connected.

The pressure reducing device, acting for reducing and regulating thepressure of the breathing gas by adapting it to the ambient pressure,therefore has a valve seat 104 interposed between a gas inlet port 117at an intermediate pressure (coming from the pressure reducing firststage) and a gas outlet port 112 at a reduced pressure.

Said bypass tube, connected to the outlet port 112, conveys thebreathing gas directly into the inhalation/exhalation mouthpiece tube102, without the gas passing inside the case 106.

Such as shown in the figures, for example FIG. 1c , said outlet port 112for the gas towards the bypass tube 101 and therefore in theinhalation/exhalation mouthpiece tube 102 is composed of a side slot 112provided in the shell wall of the hollow cylindrical element 107.

As it is known the bypass tube 101 can be outside the case (FIG. 1b ) orit can be obtained as one piece in the thickness of the wall of the case106 of said second stage 1 (FIG. 1c ).

In the embodiments shown as prior art, particularly FIG. 1b , saidhollow cylindrical element 107 passes through the wall of the case 106only at one point where it is sealingly fastened to the case 106 and itis connected, by the open end, to the gas supply conduit 103 while ithas such a length to end, by the other closed end, inside the case 106itself.

However according to known, not shown, embodiments, said hollowcylindrical element 107 can end, even by the end not connected to thegas supply conduit 103, outside the case, by an end element thatconstitutes an axial pushing assembly manually drivable from the outsideof the case 106, which pushing assembly acts on the elastic means thatis on the spring 109 that in turn acts on the shutter 108 of the valveseat 104. As it is known said pushing assembly composed of severalelements coaxial and fitted with each other in a sealing manner, forexample by O-rings, has an end outside the case, that can be held by theuser, such as a knob, and one end inside the case, abutting against anaxially slidable abutment for the spring 109, such that a rotation ofthe external part causes said abutment to axially translate andtherefore leads to a different pre-load condition of the spring 109 onthe shutter 108 of the valve seat 104.

FIGS. 1a, 1b, 1c therefore show a pressure reducing second stage 1 forunderwater use provided with a bypass tube 101, according to the priorart and wherein, considering the second stage 1 used by a user in theupright position, the inlet for the breathing gas in the case 106 andthe hollow cylindrical element 107 are arranged on the right or leftside of said case 106, that is at the side with respect to theinhalation/exhalation mouthpiece tube 102.

FIGS. 2 to 10 on the contrary show other embodiments of a second stage 1according to the present invention.

Such as shown in FIG. 2 in the second stage of the present invention theinlet for the breathing gas in the case 106 is provided in the lowerportion of said case 106, considering the second stage 1 used by a userin the upright position and the hollow cylindrical element or pipe 107of the pressure reducing device is connected to said inlet on the case106 such that its longitudinal axis is vertical or substantiallyvertical and perpendicular to the longitudinal axis of theinhalation/exhalation mouthpiece tube 102.

For illustrative and descriptive simplicity purposes, in the text theterm “hollow cylindrical element or pipe 107” means both a hollowcylindrical element 107 provided outside the case 106 and a hollowcylindrical element 107 integrated into the case 106 it being like alower hollow extension of the case 106 itself.

According to the present invention the case 106 is provided with asecond exhaled gas exhaust outlet 113 with a non-return valve 123: suchas shown in FIGS. 4 and 5 the two exhaust outlets 113 are placed at thesides of the breathing gas inlet in the case 106 connected to saidhollow cylindrical element 107 of the pressure reducing device.

The two exhaust outlets 113 facilitate the exhaled gas to come out fromthe case 106, in practice by halving the breathing effort in water withrespect to a conventional scuba regulator.

The second stage 1 of the present invention can be provided with abypass tube 101 for conveying the incoming breathing gas, upon theopening of the pressure reducing valve, directly from the supply conduit103 to the inhalation/exhalation mouthpiece tube 102, by-passing theinner chamber of the case.

Such as shown in the figures said bypass tube, considering the secondstage as used for breathing by a user in an upright position, is locatedat the rear part of the second stage 1, that is in the part of thesecond stage 1 opposite to the deformable diaphragm 111 that forms apart of the outer wall of the case 106.

According to the shown embodiment the bypass tube 101 is composed of ahollow cylindrical element provided outside the case 106 but it is alsopossible to provide said tube 101 to be made as a hollow cylindricalelement integrated in the case 106 it being like a rear hollow extensionof the case 106 itself.

Such as shown in FIGS. 6 to 10 the bypass tube 101 is connected, at oneend thereof, to an outlet port 112 provided on the shell wall of thehollow cylindrical element 107 of the device reducing the pressure ofthe breathing gas, and at the opposite end to an port 112′ provided onthe shell wall of the inhalation/exhalation mouthpiece tube 102.

With the valve seat 104 in the open position, the pressurized gas fromthe supply conduit 103 can enter into the hollow cylindrical element 107and pass, through the port 112, into the bypass tube 101 and then go,through the port 112′, into the inhalation/exhalation mouthpiece tube102.

According to one embodiment shown in FIGS. 7 to 10 a portion of the port112′ provided on the shell wall of the inhalation/exhalation mouthpiecetube 102 is surrounded by a wall protruding into saidinhalation/exhalation mouthpiece tube 102 and it bends in the directionof the port of the mouthpiece tube 102 opposite to the port inconnection with the case 106 such to form a cap-like wall 121 above saidport 112′ which cap 121 conveys the breathing gas from the bypass tubetowards the user mouth.

FIG. 6 shows a section of a pressure reducing second stage 1 with abypass tube 101 free from said cap-like wall 121 while FIG. 7 shows asecond stage 1 with a bypass tube provided, inside saidinhalation/exhalation mouthpiece tube 102, with said cap-like wall 121,with the aperture facing the portion of the mouthpiece tube 102 incontact with the user mouth when using the second stage 1.

According to a further embodiment shown in FIGS. 8-10 it is possible toprovide said cap-like wall 121 to extend longitudinally for a givenportion inside said inhalation/exhalation mouthpiece tube 102 such toform inside said mouthpiece tube 102 a tube extending lengthwise of themouthpiece tube 102 and placed at the lower shell wall of theinhalation/exhalation mouthpiece tube 102, considered in the commoncondition of use.

FIG. 5 shows the port delimited by the shell wall of said tube 121extending for a given portion inside the inhalation/exhalationmouthpiece tube 102: as it is clear from the figure the port of the tube121 is faced towards the portion of the mouthpiece tube 102 retained inthe mouth by the user by a mouthpiece 105 such to convey the gas fromthe bypass tube 101 to the user mouth.

Said cap-like wall and particularly said tube 121 allow the Venturieffect inside the inhalation/exhalation mouthpiece tube 102 to beregulated in order to improve the breathing effort and to make morenatural and simple breathing in water.

According to one embodiment said tube 121 inside theinhalation/exhalation mouthpiece tube 102 has a length ranging from 5 to10 mm.

It is possible to provide said tube 121 inside the inhalation/exhalationmouthpiece tube 102 to have a length equal to 7 mm.

Such as shown in FIG. 10, the portion of the tube 121 facing the port ofthe pipe 102 opposite to the port for the connection with the case 106has an enlargement flare.

Said enlargement flare can have an angle ranging from 5 to 15°.

According to one embodiment said enlargement flare has an angle of 10°.

The length of 7 mm of said tube 121 with a flare of 10° allows theVenturi effect to be optimized in order to improve the breathing action.

The present invention relates also to a pressure reducing second stagesuch as that shown in FIGS. 1a, 1b and 1c that is a second stage wherethe inlet for the breathing gas in the case 106 connected to a breathinggas pressure reducing device is provided, considering the second stageas worn by a user in the upright position, on a side portion of the case106, and wherein the port 112′ of the bypass tube 101 provided on theshell wall of the inhalation/exhalation mouthpiece tube 102 issurrounded by a cap-like wall 121 as described above or said wallprojects inside the mouthpiece tube 102 such to form a tube 121extending in the lengthwise direction of the mouthpiece tube 102 andplaced at the lower shell wall of the inhalation/exhalation mouthpiecetube 102.

FIGS. 11 and 12 show a variant embodiment wherein unlike the previousembodiments the bypass tube comes out flush with the inner shell wall ofthe inhalation/exhalation mouthpiece tube 102. In FIGS. 11 and 12 as inFIGS. 13 and 14 the parts of the pressure reducing second stage havingthe same configuration and/or function are denoted by the same referencenumerals as in the figures about the previous embodiments.

In the inhalation and exhalation mouthpiece tube 102 at the diameter andwith an orientation transverse to the axis of the bypass tube 101 atongue 200 is provided. This latter has a substantially flat shape andit extends in a position substantially parallel to the transverse planeof the user head in the upright position and with the second stage inthe worn condition that is in the position of use. The term transverseplane has to be meant as corresponding to the definition of sectionalplanes of the human body defined in the medical field.

The tongue 200 axially extends from the end of the inhalation andexhalation mouthpiece tube 102 opposite to the case of the second stageand it ends in a position radially overlapping the outlet port of thebypass tube 101 in said mouthpiece tube 102.

In the embodiment of FIGS. 11 and 12, starting from a given axialdistance from the edge of the tongue 200 at the end of theinhalation/exhalation mouthpiece tube 102, the tongue takes a cap-likeor concave shape 202, the side axial edges protruding downwards for theremaining lengthwise extension of the tongue and ending by a closed headside with a rounded shape 203 at or radially overlapping the outlet portof the bypass tube 101.

Along said side axial edges having the protrusion towards the side ofthe mouthpiece tube associated to the bypass tube, the tongue has suchan extension in the diametral direction that said edges are spaced fromthe inner wall of the mouthpiece tube 102, the tongue being fastened tosaid walls only by the end portion where it is substantially flat andstarting from the end of the mouthpiece tube 102 opposite to the case ofthe second stage.

The tongue according to such embodiment can have a plan shape like theone of FIG. 15 or 17 or of FIGS. 18 and 19. In such examples the tongue200 has a flat part 204 placed at the end of the mouthpiece tube 102 andextending up to the region radially overlapping the outlet port of thebypass tube by an appendage 205.

Such appendage can be made like a cap, half-cap, spoon or the like andgenerally it has a convex shape closed by a side wall oriented towardsthe outlet port of the bypass tube on the two axial sides and on the endside opposite to the flat part of the tongue.

FIGS. 18 and 19 show top and bottom perspective views of a series ofthree different tongues with cap-like appendages 205 that are differentfrom each other as regards the size that is the dimensions both in theaxial and radial direction of the inhalation/exhalation mouthpiece tube102.

According to a constructional characteristic not shown in detail, thetongue is fastenable in a removable manner inside theinhalation/exhalation mouthpiece tube 102, by means of coupling meanscooperating with axial straight portions of the two opposite side edgesof the flat part 204 of the tongue 200.

They can be any coupling means such an snap means, by elastic force, orby coupling teeth and grooves and the person skilled in the art canchoose among the several variants available in his/her common knowledge.

An advantageous embodiment provides along opposite sides of the innershell wall of the mouthpiece tube 102 a pair of guides, for example inthe form of two ribs radially projecting inwards and spaced from eachother to an extent corresponding to the thickness of the tongue. Theycooperate each one with one of the side axial edges of the tongue andpreferably of the straight portion.

The locking can take place by the elasticity of the material of themouthpiece tube 102 and by the fact that the distance between axial ribsforming the guides cooperating with the axial edges of the tongue isselected such to generate an elastic force fit of the tongue. Thelocking force can be selected such that the fastening in place isreliable, while being it possible to manually remove the tongue.

As it is clear from FIGS. 18 and 19 when the tongue is not firmly fittedin the mouthpiece tube, but when it is possible to remove and replaceit, it is possible to associate to the pressure reducing second stage ofthe present invention a series of tongues different from one another asregards configuration and/or dimensions and that can be fittedalternatively to one another. This guarantees the operating conditionsof the second stage to suit the user in a tailor-made manner above allas regards efforts necessary for breathing.

The series of tongues can be sold as a kit associated to the scubaregulator or as an accessory.

FIG. 16 shows a variant embodiment of the tongue 200. In this case therear leading edge 201 that is the edge facing the air stream coming fromthe second stage towards the mouthpiece tube 102, is slightly curved inthe direction of said outlet port of the bypass tube. Said curvature ispreferably made according to an axis of curvature diametral and parallelto the tongue 200.

FIGS. 13, 14 and 20, 21 like FIGS. 11 and 12, 15 e 17 and 18, 19 show avariant embodiment of the tongue 200. The arrangement and orientation inthe inhalation mouthpiece tube 102, as well as the extension in theaxial direction thereof are substantially the same as those in theembodiment according to FIGS. 11 and 12.

However in this case, the appendage 205 like a cap or similar shapeextends with a protruding portion 206, substantially straight andoriented with its longitudinal axis in the direction substantiallyparallel to the axis of the inhalation/exhalation mouthpiece tube 102towards the edge of the flat part 204 of the tongue, ending at a givendistance from said edge.

Said protrusion 206 can be made in the form of two opposing and coaxialcurved tongues 1206 that start from the lower side of the flat part 204of the tongue. In particular the two opposing curved tongues completewith each other such to form a channel with a curved wall like acircular sector symmetric with respect to the plane perpendicular to theplan extension of the flat part of the tongue, axial and central withrespect to the diametral extension of the tongue.

Moreover in one embodiment the lower side of the flat part 204 of thetongue is substantially tangent to said curved wall of said channel.

Still according to one embodiment, such as shown, the protrusion 206 hasa radius higher than that of the appendage 205 with which therefore itis connected by a frustum conical shape of said appendage.

By means of said protrusion 206, the baffle, that is the tongue 200according to such variant embodiment guarantees higher performancessince it collects and conveys a greater amount of flow to the mouthpiece105, therefore causing the diaphragm region to be sucked more thusresulting in a greater aperture of the valve.

Obviously also for such embodiment the characteristics about the methodsfor fastening or coupling the inhalation/exhalation mouthpiece tube 102are valid and the possibility of providing several variants differentfrom each other as regards dimension characteristics of the basearrangement are valid.

Still according to a further characteristic in common to the embodimentsof the tongues 200 according to FIGS. 18 and 19 and 20, 21 the leadingedge of the tongue 200, that is the edge of the substantially flat part204 facing the inside of the second stage is made as curved in a mannersymmetric to the central axis parallel to the axis of theinhalation/exhalation mouthpiece tube 102 and it starts with an initialsubstantially radial and straight portion at the respective sides edgesby protruding towards a common vertex coinciding with a point along thecentral axis of the outer surface of the appendage 205 by a curvedportion.

The invention is not limited to the embodiments described above butvariants and/or changes can be made to the second stage of the presentinvention without departing from the described and claimed inventiveconcept.

The invention claimed is:
 1. A pressure reducing second stage (1) forunderwater use comprising: a case (106) provided with a breathing gasinlet and with an inhalation/exhalation port through which breathing gassupplied into the case is inhaled by a user and through which the usersupplies exhaled gas into the case, said case (106) being furtherprovided with a first exhaled gas exhaust outlet having a non-returnvalve, the inhalation/exhalation port being connected to aninhalation/exhalation mouthpiece tube (102) through which the breathinggas is inhaled by the user and through which the gas is exhaled into thecase (106), the breathing gas inlet in the case (106) being connected toa breathing gas pressure reducing device provided with a hollowcylindrical element (107), said hollow cylindrical element (107) havinga breathing gas inlet port (117) communicating, through a valve, with agas supply conduit (103), said valve being interposed between saidsupply conduit (103) and said inhalation/exhalation mouthpiece tube(102) for said breathing gas, said case (106) being further providedwith a pressure sensitive device that controls opening and closing ofsaid valve, wherein the breathing gas inlet in the case (106) isprovided in a lower portion of said case (106), and wherein a secondstage (1) used by the user in an upright position and said hollowcylindrical element (107) of the pressure reducing device is connectedto said inlet on the case (106) to have an axis that is vertical orsubstantially vertical, with reference to the upright position of theuser, and substantially parallel to a longitudinal axis, orcranio-caudal axis, at an intersection of a sagittal plane with acoronal plane of the user's body; further comprising a bypass tube(101), supplying said breathing gas from the pressure reducing devicedirectly into the inhalation/exhalation mouthpiece tube (102), upon theopening of the valve, the bypass tube (101) being connected, at one endthereof, to a first port (112) provided on a shell wall of the hollowcylindrical element (107) of the pressure reducing device, and at anopposite end to a second port (112′) provided on a shell wall of theinhalation/exhalation mouthpiece tube (102).
 2. The pressure reducingsecond stage (1) according to claim 1, wherein said case (106) isprovided with a second exhaled gas exhaust outlet (113) with a nonreturnvalve (123), said first and said second exhaled gas exhaust outlets(113) being placed at sides of the breathing gas inlet in the case (106)connected to said hollow cylindrical element (107) of the pressurereducing device.
 3. The pressure reducing second stage (1) according toclaim 1 wherein in the inhalation/exhalation mouthpiece tube (102) thereis provided a tongue (200) placed substantially diametrically with anorientation transverse to an axis of the bypass tube (101) and has anextension substantially parallel to an axis of saidinhalation/exhalation mouthpiece tube (102).
 4. The pressure reducingsecond stage (1) according to claim 3, wherein said tongue (200) isprovided substantially at a level coinciding with a central diametricposition of the mouthpiece tube (102) or at an intermediate levelbetween said central diametric position and an upper semi-circumferencewith reference to the second stage in a condition worn by the user andwith the user in the upright position.
 5. The pressure reducing secondstage (1) according to claim 3, wherein in said worn and uprightposition of the user the tongue extends substantially horizontally orparallel to a transverse plane of the user's head or parallel orcoinciding with a diametric plane coinciding with a greater diameter ofthe mouthpiece (105) in a condition mounted on the inhalation/exhalationmouthpiece tube (102).
 6. The pressure reducing second stage (1)according to claim 3, wherein said tongue (200) axially extends from aposition, where said tongue substantially overlaps an outlet port of thebypass tube (101) in the inhalation/exhalation mouthpiece tube (102),with one end thereof facing towards an inside of the pressure reducingsecond stage, up to an opposite end region of said inhalation/exhalationmouthpiece tube (102), facing the user and adapted to be coupled to amouthpiece element (105).
 7. The pressure reducing second stage (1)according to claim 3, wherein the tongue has one of the followingconfigurations: completely flat; or with a curved pattern at least for apart according to at least one of the two axial and radial directions oraccording to both the axial and radial directions and with radii ofcurvature different from each other and constant or variable along anangle extension of the curved pattern.
 8. The pressure reducing secondstage (1) according to claim 6, wherein said tongue (200) ends with asubstantially diametric leading edge, in a region downstream of theoutlet port of the bypass tube (101) in the inhalation/exhalationmouthpiece tube (102) and extends till overlapping said outlet port byan appendage (205) extending said leading edge of the tongue (200). 9.The pressure reducing second stage (1) according to claim 8, whereinsaid appendage (205) has different shapes and dimensions of a baseconfiguration.
 10. The pressure reducing second stage (1) according toclaim 8, wherein said appendage (205) alternatively has oneconfiguration selected from the group consisting of: a first curvatureaccording to one axis parallel to the axis of the inhalation/exhalationmouthpiece tube (102) and with a predetermined length substantiallycorresponding to an axial distance of the outlet port of the bypass tube(101) in the inhalation/exhalation mouthpiece tube (102) from a rearside of the tongue (200) and an end portion with a cap-shape, or onlyone radius of curvature around a single axis oriented in a diametricdirection with respect to the inhalation/exhalation mouthpiece tube, orin a direction parallel to the tongue (200) and to a rear edge thereof.11. The pressure reducing second stage (1) according to claim 8, whereinsaid appendage (205) has a protrusion (206) overlapping a lower side ofthe tongue (200) from which said appendage extends.
 12. The pressurereducing second stage (1) according to claim 3, wherein the tongue (200)is mounted removably in the inhalation/exhalation mouthpiece tube (102)by a cooperating system coupling the tongue with an inner shell wall ofsaid inhalation/exhalation mouthpiece tube.
 13. The pressure reducingsecond stage (1) according to claim 3, further comprising in combinationa series of different tongues (200) that have different shapes anddimensions and that are mounted alternatively inside theinhalation/exhalation mouthpiece tube.
 14. The pressure reducing secondstage (1) according to claim 1, wherein a portion of the second port(112′) provided on the shell wall of the inhalation/exhalationmouthpiece tube (102) is surrounded by a wall protruding into saidinhalation/exhalation mouthpiece tube (102) and bends toward the port ofthe inhalation/exhalation mouthpiece tube (102) opposite to a port inconnection with the case (106) to form a cap-shaped wall (121) abovesaid second port (112′), and wherein which cap-shaped wall (121) conveysthe breathing gas from the bypass tube (101) towards the user's mouth.15. The pressure reducing second stage (1) according to claim 14,wherein said cap-shaped wall (121) extends longitudinally for a givenportion inside said inhalation/exhalation mouthpiece tube (102) to form,inside said mouthpiece tube (102), a second tube (121) extendinglengthwise along the mouthpiece tube (102) and placed at the lower shellwall of the inhalation/exhalation mouthpiece tube (102), said secondtube (121) conveying the breathing gas coming from the bypass tube (101)to the user's mouth.
 16. The pressure reducing second stage (1)according to claim 15, wherein said second tube (121) into theinhalation/exhalation mouthpiece tube (102) has a length ranging from 5to 10 mm.
 17. The pressure reducing second stage (1) according to claim15, wherein said tube (121) in the inhalation/exhalation mouthpiece tube(102) has a length equal to 7 mm.
 18. The pressure reducing second stage(1) according to claim 14, wherein a portion of the tube facing the portof the mouthpiece tube (102) opposite to the port in connection with thecase (106) has an enlargement flare.
 19. The pressure reducing secondstage (1) according to claim 18, wherein said enlargement flare has anangle of 10°.
 20. A pressure reducing second stage (1) for underwateruse comprising: a case (106) provided with a breathing gas inlet andwith a inhalation/exhalation port through which breathing gas suppliedinto the case is inhaled by a user and through which the user suppliesexhaled gas into the case, said case (106) being further provided with afirst exhaled gas exhaust outlet having a non-return valve, theinhalation/exhalation port being connected to an inhalation/exhalationmouthpiece tube (102) through which the breathing gas, inhaled by theuser, is exhaled into the case (106), the breathing gas inlet in thecase (106) being connected to a breathing gas pressure reducing deviceprovided with a hollow cylindrical element (107), said hollowcylindrical element (107) having a breathing gas inlet port (117)communicating, through a valve, with a gas supply conduit (103), saidvalve being interposed between said supply conduit (103) and saidinhalation/exhalation mouthpiece tube (102) for said breathing gas, saidcase (106) being further provided with pressure sensitive device thatcontrols opening and closing of said valve, which second stage furthercomprises: a bypass tube, supplying said breathing gas from the pressurereducing device directly into the inhalation/exhalation mouthpiece tube(102), upon the opening of the valve, the bypass tube (101) beingconnected, at one end thereof, to a first port (112) provided on a shellwall of the hollow cylindrical element (107) of the pressure reducingdevice, and at an opposite end to a second port (112′) provided on ashell wall of the inhalation/exhalation mouthpiece tube (102), wherein aportion of the second port (112′) provided on the shell wall of theinhalation/exhalation mouthpiece tube (102) is surrounded by a wallprotruding into said inhalation/exhalation mouthpiece tube (102) andbends toward the port of the inhalation/exhalation mouthpiece tube (102)opposite to a port in connection with the case (106) to form acap-shaped wall (121) above said second port (112′), and wherein whichcap-shaped wall (121) conveys the breathing gas from the bypass tube(101) towards the user's mouth.